This invention relates to obtaining information about radiation sources, and is particularly useful for locating astronomical bodies.
My U.S. Pat. No. 4,090,080 (hereby incorporated by reference) described a device useful for mapping a nearby source ("near field") of radiation, e.g., a gamma ray emittig radioisotope located in a patient undergoing a medical procedure. Each slit of the collimator is defined by a pair of parallel, radiation absorbing sheets. The collimator is rotated about its axis, and detectors are arranged to measure the radiation passing through each slit in each of many angular positions of the collimator. Simultaneous equations are then solved, applying known computer techniques, to generate the desired map.
As is mentioned in said patent, honeycomb-like channel collimators have also been used for such mapping; a single picture is taken with the collimator stationary, each channel viewing a different portion of the source. Channel collimators have also been used in x-ray astronomy, where the source is so distant ("far field") that all channels receive the same radiation flux; the collimator is mounted to pivot about orthogonal axes in a raster scan pattern.
As in the near field case, a major problem in far field imaging with channel collimators is that when the channels are made narrower or longer to improve resolution, sensitivity is reduced and a long time is required for the collimator to transmit enough radiation to assemble an image.
In my pending U.S. patent application Ser. No. 921,200, filed July 8, 1978, now U.S. Pat. No. 4,205,228, (hereby incorporated byreference) there is described a far field imaging device. A collimator is rotated about its own axis while that axis moves about a fixed axis pointing toward the overall field of view of the collimator. Radiation from the source is transmitted through the collimator during each of its revolutions about its axis. The position of the collimator relative to its axis, and the angular position of the collimator axis relative to the fixed axis, at the time of each such transmission, define a response plane. Computerized data reduction is used to find the intersection of the response planes, which will be a line pointing precisely at the source. For multiple sources, there are a corresponding number of intersections.